[daves57]

330 horse 400 cu in cant even smoke the tire runs great good top end junk off the line. is the fact that it has a 2:56 open rear end the reason why. even still it should burn that tire to a crisp whats wrong 69 bird th400 tranny yt block quadrajet thanks

[PONTIAC DUDE]

Originally Posted by daves57

330 horse 400 cu in cant even smoke the tire runs great good top end junk off the line. is the fact that it has a 2:56 open rear end the reason why. even still it should burn that tire to a crisp whats wrong 69 bird th400 tranny yt block quadrajet thanks

Yes.

Try power braking it.

[johnta1]

2 things: rear gear and stock converter

Put a lower gear in or a higher stall converter and it will seem like a different animal.

[screamingchief]

Originally Posted by daves57

330 horse 400 cu in cant even smoke the tire runs great good top end junk off the line. is the fact that it has a 2:56 open rear end the reason why. even still it should burn that tire to a crisp whats wrong 69 bird th400 tranny yt block quadrajet thanks

It could even be a combination of all those things,and throw in some ignition curve tuning for good measure as well.

If the converter was fubar and layed over a bunch of the fins inside it,then there would be very poor torque multiplication from that piece.

??? mileage trans could be slipping some too.

And highway gears are just that...

Throw in a distributor with a frozen mechanical advance and yeah,any car will be a real slug off the line.

I'd start with the easy stuff,and work towards the harder stuff.

Check & confirm the ignition curve tuning first.

Then do the same for the carbs fuel curve tuning.

Then look into the converter slippage numbers next.

Then ponder any driveline changes like a better converter and more rear gearing.

There is a process to this sorta thing,gotta approach it in a methodical manner,make one change @ a time so you know the result of that change,then move on to the next area of potential gain.

Can you tell us a little more about the motor in this?

Is it 100% stock??

How many miles???

If it's a high mileage motor,then throw in some basic engine diagnostic testing as well,things like a compression test,leakdown test,and vacuum check are all good things to do to determine a given engines "health".

Bret P.

[71 Ventura II]

X2 on what Bret stated!

My Ventura came factory with a 2.56 open diff; even with the original build of the 400 with a Speed Pro .480/.480 @.050 .231/.231 cam it would spin the "One Wheel Wonder" as long and as far as my "Nerve" would allow. I'd look hard at the tune up in the distributor and carb tune. Good Luck! JD

[steve25]

I will bet that the advance in the distributor is stuck, warm the motor up then un-plug the vacume advance and toss a timing light on the motor and rev it up to 4000, and I will bet that you do not see more than 20 degrees going on!

[WARPed]

There are way too many unknowns about your car’s condition. Is this still all OEM with 100k plus miles? Or is it a fresh rebuild? Could be a simple as your disturber timing pulled back to keep from detonation because of the lower quality gas of today.

[daves57]

dont know the whole history on the engine it has a hei distributor and it drives really great i know its a stock engine no headers or cam changes believe he said top end was freshened up about 10 years ago. hell it still passes emission test for inspection every year. running 93 octane allways no knocking or pinging thats what gets me it runs so good every thing seems to be in order except for the 2;56 rear end shouldnt have to power brake it to fry that tire.

[69Farburd]

Don't want to hijack, but Bret how do you check the carbs fuel curve tuning.

[BruceWilkie]

Even my old 68 Firebird convert when it had a stock 350 two barrel(265hp) a t400 and 2.56 gear had no issue spinning a 255/60-15 tire. with power top and weight cans etc. the convertible is heavier than a hardtop. My wifes 69 bird convertible had a stock 77 400 smog motor t400 and 2.56 gear and even it spun the tire easy.(same size tire I ran) My big old 68 Catalina 400 two barrel (290 hp) 2.56 gear also spun fairly easily.

I agree with others... its probably a tuning issue.

[screamingchief]

Originally Posted by 69Farburd

Don't want to hijack, but Bret how do you check the carbs fuel curve tuning.

Best way these days is with an O2 set-up like the Innovate stuff.

Typically that can also be done @ most chassis dyno shops or such if you dont have the stand alone set-up like the Innovate or FAST O2 stuff.

Used to be a whole lot harder to accurately do such "back in the day"...

FWIW

Bret P.

[screamingchief]

Originally Posted by daves57

dont know the whole history on the engine it has a hei distributor and it drives really great i know its a stock engine no headers or cam changes believe he said top end was freshened up about 10 years ago. hell it still passes emission test for inspection every year. running 93 octane allways no knocking or pinging thats what gets me it runs so good every thing seems to be in order except for the 2;56 rear end shouldnt have to power brake it to fry that tire.

As stated above,I'd start with all the basic engine diagnostic tests just to cover my @ss and then I'd move on to the tuning chores.

Even a seemingly "good running" engine can be somewhat weaker than one might think it is based solely on how it seems to be running @ that time.

Though even those sorta tests need to be taken in the proper context.

The main thing those tests should show to indicate a healthy engine is overall uniformity on all 8 cylinders,with no abnormal conditions or such.

Just remember that there is no substitute for good solid tuning.

After the compression/leakdown/vacuum tests I'd check the timing very closely,check & confirm base and total timing first,then work on getting the curve just how you want it so it's all in by the correct RPM for the combo.

FYI,HEI's are good distributors,but they are well known for occasionally developing sticky or worn mechanical advance mechanisms,they are also pretty well known for not always having the best performance timing curves in their OE state of tune,so yeah they often need some work to get them "right" for a more performance based combo.

Likely it will be running a whole lot better after the timing gets straightened out.

FWIW

Bret P.

[mchell]

Jmho....That thing isn't going to get out of its own way with an all stock motor and 2.56 gears......especially off the line

My old stock 400 with 3.55 would NOT destroy the tires by any means.......that's the truth

Like others have mentioned......if its half way tuned, Get some gear and it will at least feel good from a start..

[Brent Flynn]

Originally Posted by mchell

Jmho....That thing isn't going to get out of its own way with an all stock motor and 2.56 gears......especially off the line

My old stock 400 with 3.55 would NOT destroy the tires by any means.......that's the truth

Like others have mentioned......if its half way tuned, Get some gear and it will at least feel good from a start..

What rear are you using with the 3.55's? 10bolt, or 12?

[mchell]

Originally Posted by Brent Flynn

What rear are you using with the 3.55's? 10bolt, or 12?

my original 71 8.2 10 bolt(no, its not an 8.5).....auburn posi...lpw cover with bearing cap preloads...seems to hold fine with my slug....MANY hundreds of 1/4 mile passes...still waiting for it to puke...

[Brent Flynn]

i had my 8.2 in my bird for quite awhile...managed 11.88/114 with it...totally original with 3.36s... My 72 Lemans Wagon has the 8.2... i have some 3.36s and 3.55s for it, along with a powertrax lockrite and a factory 4pinion posi....but, at that weight, it probably wont hold in there forever.... will most likely upgrade this year...12bolt maybe...or Big Car hoghead(early 60s)...as i have lots of go fast goodies for them, road gears too...

[lust4speed]

Just curious. Stock sized tire or have you went to a larger and wider tire?